Since Yves Rossetti and colleague's seminal report (Rossetti, et al., “Prism Adaptation to a Rightward Optical Deviation Rehabilitates Left Hemispatial Neglect,” Nature, 395(6698), 166-169 (1998)), many researchers and clinicians have studied prism adaptation for treating the neurocognitive disorder of spatial neglect (also known as hemispatial neglect, unilateral spatial neglect, visual inattention, visuospatial inattention, visuospatial neglect or visual neglect). Spatial neglect is a neurocognitive disorder affecting attentional control, spatial perception and representation, and motor action planning. Spatial neglect commonly occurs after a stroke or brain injury. Individuals with spatial neglect demonstrate a failure or slowness to respond, orient or initiate towards contra-lesional stimuli. Right-brain-damaged individuals often neglect the left side, and the left-brain-damaged neglect the right side. Individuals with diffuse brain injuries usually demonstrate left-sided spatial neglect. Individuals with spatial neglect unfortunately have poor outcomes after standard and usual rehabilitative care. Prism adaptation treatment, by contrast, provides for a promising therapy protocol effectively addressing spatial neglect post stroke or brain injury and helps patients recover to functional independence.
Prism adaptation treatment (PAT) is a visuomotor procedure involving target-oriented arm movement guided by prism-shifted vision. During a treatment session, the patient wears prism goggles while performing tasks such as reaching to targets. The treatment effect is observed after the prisms are removed when the patient re-adapts to the normal visual world. At this time, the prism aftereffect is apparent; the patient's arm movement becomes more toward the left side if he/she adapted to the right-shifting prisms. In individuals with spatial neglect, the prism aftereffect is significant, lasting longer than healthy individuals and transferred to everyday activities. Thus, PAT shows promising therapeutic effects, reducing spatial neglect's adverse impact on functional behavior.
To enhance prism adaptation and, thus, the prism aftereffect as well as therapeutic effects, it is typical in the art to use an occluder to block the visual feedback of a certain portion of a patient's arm movements during a treatment session. The occlusion can achieve the so-called concurrent or terminal exposure. The concurrent version is to occlude the initial part of arm movement, allowing the patients to see their forearm, hand, finger and the target. The terminal version is to occlude the entire arm, allowing only the final hand/finger position and the target visible.
To achieve either version of occlusion, the art uses a “prism adaptation box,” almost always fixed on a desk or workstation. Such cumbersome “box” occluders have the disadvantages of, for example, being stationary, non-moveable during prism adaptation and non-flexible to different individuals' shoulder heights. Further, patients have to stay very close to the box and sometimes are required to use an uncomfortable chin rest.
There, thus, exists a need in the art for a portable and wearable visual field occluder to provide a patient undergoing PAT with freedom of arm movement in any direction to any location without being constrained by the conventional “box” occluders.